Liquid clarification



July 13 1943- E. M. KELLY s -rAL LIQUID CLARIFICTION Filed June 21. 19412 Sheets-Sheet 1 July 13, 1943 E. M. KELLY ETAL 2,324,400

LIQUID CLARIFICATION Patented July 13, 1943 UNITED STATES PATENT OFFICELIQUID CLARIFIOATION ration o! Delaware Application June 21, 1941,Serial No. 399,058

13 Claims.

This invention relates to the clarication or purification of liquids andespecially those that are impure or polluted such as sewage, trade anddairy wastes, packing and cannery wastes. oil renery wastes, and thelike that are characterized in that some constituents thereof must beremoved irom the water before it can be either re-used or released intowater-courses like rivers and streams, or into the ocean.

Such constituents may comprise any particles of turbidity that interferewith the clarity of the water and also particles of matter of organicorigin which is not removed from the water would cause its pollution.Such constituents, in general, exist in the Waste waters in the form ofsuspended matter whose settleability ranges from normally readilysettleable solids such as grit, u-p throughvarying degrees of normallysemi-oatability and diilicult settleability to colloids and oil orgrease that are normally nonsettleable.

So one object of this invention is to devise an improved method andapparatus for the eilcent removal by reduced pressure flotation offloatable or suspended matter from liquids that contain them, Suchliquids are well exemplified by sewage. Sewage is treated usually byinflowing it to relatively large settling basins often calledsedimentation tanks or clarifiers. Sewage is held in them in quiescenceso that those suspended solids that will settle. do settle and depositon the bottom oi' the clarifier as sediment. Mechanical means areusually provided for raking the sediment from the tank bottom todischarge. These clarifiers have the size controlled by the overilowrate and detention time necessitated by the settling rates of thesuspended solids to be settled. This makes these clarier tanksrelatively large, in some cases a hundred or more feet in diameter. Someof the suspended material is iloatable, which tends to rise to thesurface o! the liquid in the clarifier and form into a disagreeablescum. The skimming of such tanks has presented a serious mechanicalproblem.

Therefore another objectr of this invention is to devise equipment thatwill remove settleable matter from polluted liquids rapidly and withoutthe necessity of the usual long detention period. whereby the equipmentcan be made substantially smaller. And a further object is to arrangesuch equipment so it will also remove floatable matter asn scum about asfast as accumulated on the surface of the liquid.

Sewage and the like polluted liquids are usually either unsightly orodoriferous, or both, so it is another object oi this invention todevise equipment for the clarification thereof that is covered wherebythe liquid being treated is maintained out of view.

A still further object oi this invention is to cause certain normallynon-oatable suspended solids to be floated with a concurrent improvementin settling the non-fioatable and normally settleable suspended solids.

The invention is preferably embodied in equipment wherein the pollutedliquid has gas diffused therein, called hereafter gassed liquid; thegassed liquid is conducted to, and released in proximity to the surfaceof, a body of liquid being treated, on the surface of which liquid thereis effective a pressure that is less than that on the gassed liquid.Normally the gased liquid is supplied under atmospheric pressure whilethe pressure on the surface of the liquid being treated issub-atmospheric, namely, under the effect of vacuum. Moving means areprovided for skimming iioated matter, including scum, foam, oil orgrease, into an arrangement that includes a dam over which the floatingmatter is removed from the zone of treament of the liquid.

Important in such an arrangement is the control for maintaining of aconstant liquid level for the body of liquid being treated, andpreferably it should be adjustable. In the preferred embodiment of thisinvention, this is accomplished by maintaining in what may be called acontrol box, a relatively small or minor body of liquid being treatedapart from the main body so as to be substantially free from scum orfloating solids but in hydraulic communication therewith at the bottomportion while in gaseous communication at its top portion with thegaseous but reduced pressure atmosphere overlying the liquid beingtreated.

Another characteristic oi' this invention is that associated with theminor or auxiliary body of liquid in the control box, there aresuction-applying means primarily for applying the effect of vacuum tothe main body of liquid which automatically cease applying suction whenexcess liquid accumulates above the desired liquid level. 'I'hese meansare exempliiied by a suction pipe or nozzle connected to a wet vacuumpump, and the pipe may also be pivotally adjustable for controlling theheight of the controlled liquid level, Clarified or treated liquid isremoved from the equipment in quantity equal to the liquid incomingthereto for treatment, so the machine is continuous in operation. Also,the clarified liquid that is removed, is derived from a zone ofmaterially lessened effect of vacuum and also from a place whereat thewithdrawn liquid is shielded from descending of settling solids.

The sequential gassing and vacuum. or reduced pressure, treatment seemsto cause not only the normally iioatable matter but importantly asubstantial quantity of normally non-floatabie and normally diillcultlysettleable suspended solids, as well as semi-floating solids, to rise orto be buoyed to the liquid surface from whence they are removed by theskimming means. Other suspended solids seem to have their settleabliityincreased, so that as a result of the vacuum treatment. solids from someliquids settle to the bottom of the tank and deposit as sediment,whereupon they are independently removed. When treating some liquids,the claried liquid can be removed from the tank through the vacuumsuction pipe, while in treating other liquids, it may be desirable toremove the treated liquid from another zone or zones of the tank.

Since it has been found that the vacuum is effective to the maximum tofloat suspended solids substantially only when they are exposed to thevacuum efl'ects at the liquid surface, it is important that the velocityof the suspended solids fed to the machine shall be such that solidsreach the region of the liquid surface of the body of liquid beingtreated. To this end, the liquid to be treated is preferably supplied tothe tank by means of a draft tube that is so calibrated and so shapedthat the suspended solids in the feed passing up through the draft-tubeare emitted therefrom into that zone in which the vacuum becomeseffective on them. The design and shape of the draft-tube should be suchas to give a velocity of the feed liquid up the draft-tube so that thereis discouraged any dropping back down in the draft-tube of settlingsolids because once they start downwardly, the pull of the vacuum is notvery strong on them. At the same time, however, the velocity of theliquid emitted from the mouth of the draft-tube should not be greatenough to cause substantial up-surge or turbulence in the liquidthereabove. The reason for this is that it causes the bubbles buoying upthe floated solids to be shaken loose therefrom, whereupon those solidsdescend and thus escape being skimmed oi! the liquid level as scum.Experience has shown that the mouth of the draft-tube can be locatedconveniently about fifteen inches below the liquid level although it canbe used vryinsly in a. range substantially between two and fifteeninches. Experience has also shown that the degree of vacuum used isimportant. Below tive inches oi' mercury, there is little ei'-fectiveness. Indeed, not less than seven inches of mercury seems to beabout the minimum degree of vacuum used, and nine inches or higher, isbest. Therefore, that latter figure is recommended. It takes 13.6 inchesof water to equal one inch of mercury. Therefore, in order to have atleast some degree of vacuum effective on all the liquid in the tank,except oi' course that on the bottom thereof. the tank should be of theorder of 9 x 13.6 inches in depth, or roughly 10 feet. In such a tank,while there is vacuum equal to about 9 inches of mercury effective onthe liquid level in the tank, at one foot below the liquid level, thevacuum equals about B inches of mercury, and so on down, each foot ofdepth taking of! about one mercury inch of effectiveness oi the vacuum.Beyond five feet or 5 mercury inches), however, there seems to be littlevacuum effect, but this is desirable i'or it leaves that zone of liquidbelowr the five foot level. in relative qulescence in which those solidsof high specific gravity settling thereto. are permitted unmolestedly toform a sediment on the tank bottom, from which they can be removed asdesired. The point oi.' their withdrawal is preferably from a regionwithin the treatment tank that is under the effect oi' vacuum equal totive inches or less of mercuryI because this assures no floatingmaterial being carried ofi. with the sediment. Discharge of materialsfrom such a machine naturally has to be through the medium of aliquid-sealed barometric or hydrostatic leg or its equivalent, forotherwise the efiect of vacuum would be lost by air-leakage.

Itis generally desirable that nothing be interposed between the liquidlevel and the effect of the vacuum that interferes with theeffectiveness of the vacuum. In order to keep the liquid level clean andclear of vacuum-obstructing material, this invention teaches that it isadvisable to remove from the liquid level scum or other floatingmaterial (sometimes called herein "fioat) about as fast as formed sothat there is no adverse accumulation thereof, and with the leastdisturbance of the underlying liquid. In order to accomplish thispersistent and non-turbulent cleaning of the liquid level, it is alsonecessary to maintain the liquid level at a constant height so thatfloating material can be constantly and effectively removed therefrom.Where skimming is important of itself, the character of the scum may becontrolled somewhat by the height of the liquid level as compared withthe effective level of the overflow weir or dam of the scum dischargearrangement. If for instance, a material being handled forms a thickcompact scum and it is desired to discharge this scum with a minimum oiwater-content, then the liquid level of the tank can be lowered to anelevation several inches below the scum overflow Weir independent of thescum discharge arrangement, through the rnedium of control features ofthe auxiliary compartment or control box with its adjustable suctionnozzles. If on the other hand, the material handled does not form acompact scum, or if its water content is unimportant, the liquid levelele vation o! the tank can then be ad-.iusted to a point from which mostor all of the float will flow by gravity over the dam into the scumdischarge outlet. One purpose of getting the scum or float out as soonas possible is so that the air bubbles attached to the solids are notdetached, for ii' detached in any substantial quantity, the buoyed upsolds will settle and so out with the effluent. The notation effectsattained by this vacuum treatment on suspended solids take place withina rather limited range of degrees of vacuum, so as much as possible ofthe fioatable material must assuredly be conveyed into that horizontallayer of liquid subject to such vacuum. This is assisted to some extentby first diffusing dissolving air or gas in the liquid fed to the vacuumtank whereby when the suspended particles encounter the lessenedpressure in the tank. the dissolved and entrained gas is released toform gas bubbles that attadhthemselves to solid particles and tend tofloat most of the suspended material into that area of limited vacuumeffect. Aeration or gassing of the liquid prior to its release into bodyof liquid being treated under the effect of vacuum. has proven to bequite satisfactory since it effects the diifusing ofthe air or gas inthe liquid, but in such a case. it is usually desirable to give theaerated liquid some de-aeratlng treatment assasoo relebse in the liquidbody in order to it substantially ail large or coalesced bubbles. Risinghibbies enlarge in ascending. and an expanding ubble tends to detachlitself from the solid that* is buoying up or floating. Therefore, thefiner or smaller the bubbles developing from the liquid under vacuum thebetter. for merely large ani-,rained air bubbles are useless for thenotation function.. In fact the large bubbles are detrimental becausethey cause undue agitation on being released. Y

Non-settleable and slow settling suspended solids interfere with thesettling of readily settleable solids, but the sequential gassing andvacuum treatment of this invention seems to pull the slow settlingsuspended solids up and out so that the left-behind non-floatable andsettleable solids can assume their normal free settling rates. Thus in amachine embodying this invention, sete tieable solids settle better. Thevacuum and the rising force exerted by the air bubbles on the suspendedsolids act likea collector, especially when there are grease or otherfoamor frothforming substances present, as is especially true in sewageand the like wastes. The vacuum apparently has a :le-aerating effect.For instance, it makes activated sewage sludge sink. It has a depressanteffect on settleable solids, although not on slick solids. This type ofaction resulting from the effect of vacuum, when sewage and the like aretreated, floats grease-bearing particles and other fioatable materialaway from the settleable inorganics, so that the sediment separated anddischarged by the apparatus of this invention is fairly clean. Thevacuum will cause to float normally non-floatable inorganic matter ofsome types such as lime sludge derived from water softening, asmagnesium hydroxide, borax, potash and the like.

With respect to the treatment of sewage, it is to be recalled thatsewage coming to a treatment plant at times has a relatively hightemperature. This, together with flat sewer grades and lons flow lines.often results in considerable anaerobic bacterial action taking place inthe sewage prior to clarlcation treatment, with the result that thereare usually present in the incoming sewage substantial quantities of gasbubbles, buoyed scum, and floating, partially-digested sewage sludge.The discharge of large quantities of cannery wastes into seweragesystems aggravates this problem and increases the floating scum. Theapparatus of this invention is quite effective on these conditions. fornot only are the scum and the sludge separated, but the sewage beingtreated in the machine is der-gassed.

The presence of finelydivided gas bubbles in sewage or other liquid hasa decidedly detrimental effect on clarification by sedimentation; so torid the sewage of its entrained gas, substantially facilitates thesubsequent sedimentation. And again, as sewage and the like wastes areusually highly odorous. the vacuum removal of this invention rids theliquid of its entrained gases and thereby reduces their odor-givingcontent.

The trade-mark 'Vacuator" has been given to and used in connection withembodiments of this invention, prior to the filing of this application,so that term for short, may be used hereinafter. A maior characteristicof a Vacuator is the vacuum removal from liquids not only oi normallyfioatable matter but also of normally non-nostable matter. A furthercharactreistic is the simultaneous independent removal from liquids ofnormally non-iloatable and of settleable susprior t its remove frompended matter desired to be removed therefrom. Thus it is a machine thataccomplishes removal of matter from the liquid by physical means indistinction from biologic or bio-chemical means. In some cases, theVacuator may be used as a skimmer only, so that scum is discharged fromit by one path, while by another path there is passed from the Vacuator.de-scuxnmed liquid with non-floatab'e solids unremoved vfrom suspensiontherein. Other uses may call for three separate discharge paths leadingfrom the Vacuator namely (l) for scum, (2) for clarifier eiliuent, and(3) for sediment or sludge. The Vacuator has proven that it can do afair job of removing suspended solids at as high an overflow rate as10,000 gallons per sq. it. per 24 hours.

F18. l is a vertical sectional view of a continuout type of apparatusfor separating and removing of suspended matter from a liquid body. Inconnection with this figure it is to be noted that a large mainseparating tank prominently appears and that a small or auxiliaryliquid-level control tank or chamber is shown at the righthand side ofthe large main tank.

Fig. 2 is a vertical sectional view of the auxiliary liquid-levelcontrol tank or chamber. In Fig. 2 the parts are shown at a larger scalethan in Fig. 1.

Fig. 3 is a horizontal sectional view taken as on the line 3--3 of Fis.2 looking in the direction of the arrows.

Fig. 4 is a pian view of the apparatus of Fig. l. In this figure certainparte of the top of a main separating tank thereof have been broken awayto show more clearly the construction of certain functional partstherein.

In the accompanying drawings'. i0 represents a main tank, II its bottomor floor, if its closed roof or top, II a scum discharge duct or pathwayhaving a barometric or hydrostatic leg il, it, an elongated edge, dam orweir that is not normally submerged, it a funnel section of the scumdis,- charge duct Il that supports the weir It and a ramp I1 leading upto the weir. II represents an opstanding draft-tube, i9 a feed inletpipe or conduit of which the draft-tube forms a functional terminal. 20represents a flared outlet section of the draft-tube l0, 2l a spidertherein by which the draittube is supported from shaft 22 rotatablypenetrating, in a gas-tight manner, the tank roof il, which shaft isprovided with a worm gear It that is rotated by a worm 24, driven by amotor 26. 2t indicates scum raking arms, extending substantiallyradially from the shaft 22, and I1 indicates scum sweeps carried by thearms Il that are adapted for scum sweeping cooperation with the ramp i1and weir IB.

30 represents generally a supplemental or auxiliary tank or compartment,which with its assembly constitutes an arrangement for applying theeffect of vacuum to the main tank i0, and also for controlling theheight of the liquid level L in the main tank. ll indicates a freelycommunicating passageway provided by a pipe extending between the uppersection of the main tank and the upper section of the auxiliary orsecondary tank 30. I2 indicates a closed top or roof on the secondarytank fil, while It indicates a liquid pathway or communicating pipeextending between the bottom Il of the tank 30 and to the interiorliquid-holding portion of the main tank I0.

3l indicates a wet-vacuum pumping means for sucking air or gas from theinterior of the secondary tank 30 by such conduit means as a pipe Ilthat terminates in an adjustable inlet end or noazlell. Y, Pipe 38 andnozzle 3l can be duplicated as shown. It duplicated both pipes 38 willmerge into a single pipe 38 lea/ding to the pump Il. The inlet ends ornozzles 31 are pivotally adjustable by means of hand-operated shafts l!that extend through the casing of the second tank 30. lli indicates avalve that can be inserted in each suction pipe 36. 4l indicates adischarge pipe 1ine extending from the vacuum pump 35, as shown. l2indicates a port-hole or; inspection glass in the top of the secondarytank 30. Il indicates a water iet or spray to which water is supplied bypipe I4 tha.t is controlled by valve 4I, for washing the underside ofthe glass l2 free or scum accumulations thereon. ll indicates a gaugeglass on the tank 30. A protected electric light Il may be locatedwithin the tank 3l adjacent the port-hole glass 42 to illumine thecontents of the tank tor better view thereof through the port-hole.

I indicates baming means within the main tank i0 forming a ring-like orannular eiiluent take-oil system for the main tank, for shielding thewithdrawn liquid from descending or settling solids at the place ofwithdrawal of the eiiiuent liquid from the liquid body in the tank. Thisis preferably provided with a downwardly inclined top member Il, acylindrical member I2, a horizontal closure member il having aperturesIl therein located at intervals. 55 indicates a treated liquid, oreiiiuent take-oft discharge pipe valved at 5I' that is provided with abarcmetric or hydrostatic leg 56 that dips into a basin or pool 5lformed by means of an adjustable dam or Weir 58. over which liquid flowsto discharge through eliiuent discharge pipe 59.

Fig. 1 shows an optional assembly or sediment or sludge rakingmechanism, supported from and rotating with the draft-tube i8. Itcomprises rake arm B3 extending generally outwardly from the draft-tubeIB (and, if necessar braced with tie rods as shown) that are providedwith sediment or sludge impelling or plowing means such as blades, rakesor edges 6I, which incident to travel thereof adjacent the tank bottomor floor Ii, impel sediment towards and into sludge sump 6i, from whichsediment can be discharged through pipe 66 and pump $1 downwardlythrough pipe 68 leading to a no-pool part l2 of the depressed sump 69.

Sump' or wet-well 69 has in its bottom section an adjustable dam or weirin for forming a basin or pool H adapted for the sealing barometricallyof the leg I4 of the scum discharge duct system Il. In the non-pool partl2 of the sump 69, a pipe i3 reaches thereinto associated with which isa pump 14 for conveying the scum and sediment to further treatment ordisposal. T6 indicates a pipe through which hows the impure or pollutedliquid supplied for treatment. This pipe Il delivers the liquid into awet-well or sum1) l1. wherein the liquid passes under an adjustablecurtain baille 18. 19 indicates a gassing station or gas diffusing meansfor causing gas or air to be dissolved and entrained in the incomingliquid. In the drawing it is shown as a diil'using or gassing impelleron a shaft driven by a motor 8U. Il indicates a de-aerating orde-gassing lowthrough passage or channel, in Awhich there is anadjustable height weir B2 over which the liquid cascades before enteringthe Vacuator feed pipe I8. This passageway Bi is for de-aerating theliquid to rid it of enlarged entrained gas bubbles.

II indicates a cover on the de-aerating p way to make the apparatussightly. I4 indicates a all liquid is discarded through pipe I9.

9U represents a manhole cover in the top i2 of the tank IU for entrancepurposes. an electrical light for illuminating the interior of the tankIll. 92 indicates a glass-bearing porthole in the top o! the tank I0 forvisual inspection purposes, and 83 indicates a water iet or nozzle,supplied from pipe 94 with its valve Il, for washing scum from theunderside of lthe glass of the port-hold 82.

It is to be observed that the inlet pipe Il to the tank lil has as itsvertically-extending terminal the draft-tube Il.

entrained air, are de-aerated from the liquid in the passageway Bi. Thegassed and de-aerated the control assembly 3D. The liquid rises in thecontrol or secondary tank or compartment 30 through the pipe 33. Thevacuum pump 35 in exerting a gas-exhausting suction throughnozmunicating passageway or pipe 3i that extends between the uppersections of the main and secondary tanks.

Th liquid level L in the secondary Vtank 3l is is discarded through pipe4i. It is to be noted that the minor body of liquid being treated thatis hydrostatically contained within the secondary tank 3i! is shieldedfrom having any scum or floating material reaching it, because it isconnected to the main tank at a point below which the scum has beenreleased.

Liquid passes up the draft-tube in the main tank in and is emitted mtsthe bdy'of liquid in the tank at a. diminished velocity, due to theflare 20 of the draft-tube IB. The velocity is diminishedv so that thereis substantially no turbulence created above the draft-tube and itsflared section, namely, in the liquid that is there located.

The tube-type of delivery oi' feed liquid is for avoiding as much aspossible dispersion Aor diffusion of the vacuum-floateble particles inthe liquid body of the tank prior to'realizing the lifting efl'ect ofvacuum on them. Y

The avoidance Vof turbulence, in this rather critical zone ofV vacuumaction, isdesirable as tur-1V bulence is disdvantageous to notationsince it tends to shake bubbles loose from the solids to which thebubbles have become attached'. soonas the liquid is released from thedrafttube i8, the lessened pressure or eileetof vacuum, causes thedissolved and finely divided entrained gas in the liquid to come out oithe solution, whereupon bubbles oi gas are developed that cling tosuspended solids encountered by the gas bubbles. In sewage and the likewastes, there is enough oil and grease onftlfiesuspended solids to actas an adhesive to cause the bubbles to adhere to the solids, `whereuponthe bubbles cause the solids to which they are attached to be buoyed upand to float to the liquid level L, VAccumulation of the iloated solidsforms a floating layer of` scum.

It is desirable to continually remove the scum to leave the liquid levelas free thereof as possible. To this end, the scum arms 26 are rotatedwith shalt 22 from motor 26. The scum arms with their sweeps 26 pushscum in front of them until the ramp 21 is encountered, when theA sweeps21 in riding up lontothe ramp, puslthe scum beiore them, and over thescum dam i5. The scumialls from or cascades over the dam into.thertunnel section i6 of the scum removing duct means that includes thepipe I3, through which pipe plus its barometric leg Il, the scum isdischarged from the main tank l and into the pool or basin 1l in amanner which prevents any air leakage into the tank I0 to otherwisespoil or diminish the vacuum therein.

Liquid from which the'floatedmaterial has been removed, is discardedfrom the tank as treated liquid or eluentthrough the eilluenttake-off'assembly 50, by rising upwardly through the apertures Bl intotheannuldr'bailled space, from whence it flows to discharge through pipeE5, which also is a barometrlc leg since it terminates in pool 51, toprevent air leakage into the tank lll. The assembly Eil shieidsthedrawn-off eilluent from descending or settling solids, and the assemblyis located at a depth in the tank at which the eilect of vacuum is equalto the order oi 5 inches of mercury. It is the place or region wherethere is a minimum ofrrsuspended solids and a minimum of sedimentedsolids. In those cases where the Vacuator is to be used only to cle-scumthe liquid to be treated. the eilluent takeoff will constitute the onlyother discharge duct from the tank besides the scum removal duct. Insuch an instance, the ellluent liquid will have entrained in it, thosesuspended solids that have escaped or been immune to the flotationeffects oi the vacuum. Y A

However, in other cases, it will be desirable to make a furtherseparation by riding the eilluent liquid of its suspended solids thathave escaped the vacuum notation. This can be accomplished in theembodiment of the invention shown because the suspended solids that haveescaped ilotation will descend and settle on the floor Il of the tanklll by sedimentation processes, Vand will accumulate as sediment on thedoor. The sludge rakes 64 in being moved at speeds that have asubstantially non-rolling eilect on the sediment, by the travelling rakearms BI due to rotation oi the shaft 22 and draft-tube i8, will impelthe sediment inwardly toward the center of the tank in Vuntil thesediment reaches the V sludge sump Bl, from whence the sedimentorrsludge can be removed by the pump ,B'IAY andkdiscarded through pipeB8 into the sump l2. such acaso, it can be seen that thesediment and theemuent liquid are discharged from the tank I0 by separate andindependent paths. The level at which the eilluenty take-oi! is locatedis deep enough in the tank to be at a point where the effect of vacuumis so slight that practially vall floating material is thereabove, forit is quite important that no, or substantially no, heating materialpass from the tank with the treated emuent. More particularly, thelocation of the -eiiluent take-ofi should be sumclently below the liquidlevel oi the tank that the etlect of the vacuum at that take-oil' levelis less than or equivalent to not substantially more than 5 inches ofmercury, Since the feed to the vacuator is continuous, and the scum andthe eilluent take-ods are continuous, the operation of the machine iscontinuous, and the liquid being treated in the vacuator is anever-changing body of liquid. The sludge can be taken out intermittentlyor continuously as desired.

.From the sump 12 the mixture of discharged scum and sludge can beconducted, through the medium oipumpu, for further treatment such as byanaerobic or other biologic digestion. The eiiiuent of treated liquidpassing out oi the pipe I5 and its barometric leg Il is then availablei'or release or for further treatment, as may be desired.

As the liquid level in the main tank lil is controlled .by the adjustedheight of the suction nozzles $1 in the secondary tank or compartmentil, by the adjustment of the nozzles 31, the liquid level in the tanklll can be raised or lowered re1- atively to the height of the scumoverflow dam l5. Ii the discharging soumis desired to be dewatered asmuch as possible, then the liquid level is droppedsomewhat below thescum dam I8. On

the other hand, in order to make the discharging scum more i'luid, itmay be desirable to have more water go out with it, in which case theliquid level in the tank l0 is raisedrwlth respect to the scum dam, bymeans orisuitable adjustment oi' the pivoted vacuum suction nozzles 31.

A Vacuator may be looked upon as an eillcient substitute, at least inmany instances, for a present-day mechanically-cleaned clarifier, forexperience hasshown that a Vacuator is eective in riddlng the liquidbeing treated of a substantial portion of its suspended solids in aboutthe `proportion of '75% of iioated suspended solids fifteen minutes maybe used, as appears requisite. This represents an enormous saving insize as compared with an ordinary clarifier.

Initial operatiomior starting up .a Vacuator can be carried out by oneof two methods. The preferred method is to close all valves Il and Il onthe inlet and outlet piping respectively so that the tank ill can befilled by a pump (not shown). When the water level reaches the'elevationoi the scum dam il, the pumping can be discontinued, the airoutletconnections closed, to wit, air outflow pipes controlled by valves III'the vacuum pump e! started. and as soon as the vacuum gauge used inconnection with the pump Il registers equivalent to the hydrostatic legin the tank, valves Il and 8l' in the inlet and outlet pipingrespectively can he opened simultaneously, and dow through the invertedsiphon Il and il will automatically start. Obviously all hydrostaticlegs must be kept sealed with liquid.

The respective water levels Ain the feed and einuent compartments willautomaticallyV adjust themselves, depending l10n the loss of headthrough the unit and the elevation of the overiiow weir in an emuentbox.

The other method of starting consists in maintaining sufilcient water inthe vhomies or pools in which the hydrostatic legs are located, startingthe vacuum pump and thus pulling the water up into the tank as theabsolute pressure is decreased.

For shut-downs of several hours duration, all valves in the inlet andoutlet piping can be closed when the tlow has stopped, and the vacuumpump can then be shut down without emptying the tank contents. Forshut-downs of longer duration, the device can be emptied by stopping thevacuum pump and admitting air slowly through a suitable valve in thetank cover.

The normal adiustments obtainable during regular operation consistsprincipally of:

l. Control of water level elevation; and

2. Speed variation of skimmer mechanism.

If for instance a material being handled forms a thick compact scum andit is desired to discharge this scum with a minimum water content. thenthe water level in the control box should be adjusted by raising orlowering the nozzle to an elevation several inches below the scum dam.If, on the other hand, the material handled does not form a compact scumor its water content is not important, the water-level elevation canthen be adjusted to substantially that of the scum dam so that most orall of the scum will new into the scum outlet by gravity. usual cases itmay be advantageous to raise the water level above the scum dam.

The presence of nnely-divided gas bubbles in sewage or other liquid hasa decidedly detrimental effect on clarification by sedimentation; so torid the sewage oi its entrained gas, substantially facilitates thesubsequent sedimentation. And again, as sewage and the like wastes areusually highly odorcus, the vacuum removal oi this invention rids theliquid of its entrained gases and thereby reduces their odor-givingcontent.

In the gassing, or diffusing of a gas in sewage, it has been found thatsewage and certain other polluted waste liquids, have an oxygen demand.This is commonly referred to as B. O. D., which is an abbreviation ofbiochemical oxygen demand. Il' one attempts to diii'use air in such aliquid, the oxygen demand is so great that instead of the air beingdissolved or entrained in the liquid, the oxygen of the air enters intochemical combina-- In some extreme or u'ntion, with the result that whenthe aerated liquid gets into the scum flotation apparatus, the lessenedpressure on the liquid falls to develcr gas bubbles as it would. due tothe air comin? out of solution and entrainment. Consequently it isproposed by this invention, in connection with oxygen demanding liquids.to practice the gassing step heretofore described, by the use oi somegas that is inert to the oxygen demand of the liquid. For instance, inthe treatment o'i sewage, it has been found that the gassing step can besatisfactorily carried out by the use of carbon dioxide (C02) gas. Thishas the advantage not only of being readily soluble in the sewageliquid. but upon encountering the lessened pressure, due to the eiiectof vacuum in the scum noating apparatus, the CO2 comes out of solutionand develops a maximum ci' very small bubbles, that are highly eectivefor flotation purposes.

Since the solubility of nitrogen in water is twice that of oxygen. it isindicated that a nitrogen bearing gas can well be used. Of course, ifthe gassing be done with a gas other than air, the gasslng must be donein a manner so that the gas is not allowed to be wasted. so under suchconditions. the gasing station 19 would have to be provided with a pipeor duct iilli that conveys the CO: or other inert gas for releasedirectly into the agitation zone of the aerating or gassing element 10.The point of this feature oi.' this invention is the supplying, to anoxygen demanding liquid. of a gas that is inert to the oxygen demand ofthe liquid. Maximum solution and entrainment of the gas in the liquid isdesired with a minimum of chemical reaction of the gas with the liquid.

We claim:

l. The process of removing suspended solids from their carrying liquidwhich comprises maintaining an enclosed body of liquid being treatedwhose liquid level is subject normally to vertical fluctuations,continually supplying gas-containing liquid to the liquid body andconducting such liquid to the region of the surface ci the liquid body,continually sucking liquid through a pipe inlet disposed cooperativelywithin the limits of the iluctuating liquid lever alternately liquidwhen the liquid level rises thereabove and gas when the liquid levelfalls therebelow whereby to substantially minimize nuctuations of thelevel of the liquid body and whereby to continually maintain on thesurface of the body sub-atmospheric pressure, continually removingiloating matter from the surface of the body at a point functionallyremote from the point of applica tion oi the suction, and continuallyremoving from the body claried liquid.

2. The process of removing suspensions from a liquid bearing them whichcomprises establishing and enclosing liquid divided into a maior liquidbody and a minor liquid body with both bodies having a common atmosphereand with liquid in the minor body having a vertically iiuctuating liquidlevel, supplying feed liquid to the major body, removing iloating scumfrom the maior liquid body, discharging eiiiuent from the enclosedliquid from a-place functionally remote from the floating scum. suckingliquid from the minor body when the liquid level thereof rises above apredetermined elevation, and sucking gas from above such liquid when thellquiduevel thereof falls below such predetermined elevation.

3. Apparatus for the removal oi suspensions from a liquid bearing themwhich comprises a closed tank adapted to bold a liquid body whose levelnormally varies, leed-liquid tube means having aftenninal endingwithin-the tank by Ywhich liquid Visfs'uppliefd' thereto; conduit meanshavingV an inlet for removing'ffrom the tank material iioating at theliquidlevel thereof, means for maintaining on' the liquid in the'tankfagaseous medium at sub-atmospheric pressure including means-having aninlet extending cooper-Y suction atively within the range of variationsof the liquid l'evel and independent of the noati'ng material removingmeans adapted to pump liquid through the suction means when the liquidlevel rises thereaboveang thus controlling the liquid level oi.' thetank, fand'means'lor Vretrieving treated liquid .from the tank having an-inlet in the tank that isV disposedffunctionally remote from theinletto the'floating material removing meansY 4. Apparatus according toclaim 3, including means prtwidingV anjauxiliary compartment associatedwith Ythe tank for holding in its lower portion liquid derived from theliquid of the tank and having its topV portion in gaseous communicationwith the space above the liquid in the tank. with the addition that theinlet of the suction means is adjustable; and is associated with theauxiliary compartment for controlling the liquid level of the liquidtherein.

5. Apparatus for the removal of suspensions from liquids comprising aclosed tank adapted to hold a liquid body having a normally verticallyuctuating liquid level, tube means by which gassed liquid may be fedinto the tank and delivered in the region of the surface level of theliquid in the tank, combined wet and dry suction means adapted tomaintain sub-atmospheric pressure within the tank including a pipehaving an inlet disposed within the vertical limits of the uctuatingliquid level, and a pump connected with said pipe effective to drawliquid therethrough when the inlet is submerged and to draw gastherethrough when the inlet is unsubmerged, a scum-discharge ductleading from the tank including a liquid seal thereon exteriorly of thetank, means for sweeping floating scum into the scum duct, and means forconducting treated liquid from the tank including a liquid-sealed lowerend outside the tank.

6. ,Apparatus according to claim 5 with the addition of a dam providedat the upper intake end portion of the scum discharge duct over whichfloating material must pass before entering said duct. and wherein saidsuction means includes adjustable means for varying the liquid levelrelative to the dam.

7. Apparatus for removal of impurities from liquids comprising a.cllosed tank adapted to hold a liquid body, tube means by whichgas-containing liquid may be fed to the tank and delivered at the regionof the liquid level in the tank, suction-producing means for maintainingvacuum Within the tank. a scum-discharge duct including a dem at theupper end thereof and having a liquid-sealed lower end, means forsweeping iloating material in the tank over the dam and into the scumduct, means for removing treated liquid from the tank at an elevationlower than that of said dam and having a liquidsealed lower end, saidsuction-producing means having a positionable suction inlet disposed atan elevation proximate to that of the upper edge of the dam andeilective to control the relative height between the liquid level of thetank and the dam.

8. Apparatus according to claim 'I wherein the neat-sweeping meansis'iunctionally sepa.- rated from thepositionable suction inlet.

t afpparatusffo removal ofsuspended matter from liquid comprlsingga tankadapted to hold a main bodyof liquid being treated, tube means leadinginto the tank and having a terminal from which gas-containing liquidbeing treated is delivered within the tank, means for maintainingadjacent the main liquid body a second body of liquid whose liquid levelis subject to vertical iluctuatlons and which has a common atmospherewith the main body, means for conneeting the-atmosphere of the secondbody with that of the main body. means providing a passageway forow ofliquid from one body to the other: means for removing from the tankmaterial floating on the main body, means for removing treated liquidfrom the tank. and suction means essentially embodying a Kgas-liquidpump and a pipe having an inlet disposed cooperatively within thevertical limits of the uctuating level of the second liquid body servingfor alternately withdrawing liquid through the pipe inlet when submergedand gas when unsubmerged for thereby controlling the liquid level of thesecond liquid body as well as for applying vacuum to the commonatmosphere of the main and second liquid bodies.

10. Apparatus for the treatment of liquids having suspensions thereinwhich comprises a closed tank adapted to hold liquid with at least aportion of which whose liquid level lluctuates vertically, tube meansterminating in the tank for supplying gas-containing feed liquidthereto, scum-receiving means having an inlet disposed to receivefloating scum, means for passing scum from the tank through saidreceiving means while minimizing leakage of air therethrough, suctionmeans leading from the tank having an inlet disposed functionally remotefrom the scum inlet but within the range of fluctuations of the liquidlevel for sucking liquid when the inlet is submerged and gas whennonsubmerged whereby sub-atmospheric pressure is maintained on the tankliquid,eflluent discharge conduit means leading from the tank having aninlet section that is disposed functionally remote from thescum-receiving means, liquid-seal means exteriorly of the tankassociated with the eilluent discharge means for minimizing leakage ofair therethrough, and means for shielding from suspended and settlingsolids the inlet section of the conduit means.

ll. Vacuum flotation apparatus comprising a. closed tank adapted to holda body of liquid therein having a liquid level, feed inlet means havinga rotatable feed-emission terminal and a fixed delivery section leadingthereto by which gas-containing liquid suspension is fed into the tankand released into the liquid body at the region of the surface levelthereof, suction means for applying sub-atmospheric pressure to the`surface of the liquid in the tank, a scum-discharge duct leading fromthe tank proximate to the liquid level therein, means for sweepingfloating scum thereinto, a motor-driven shaft extending vertically intothe tank. conduit means leading from the tank for conducting treatedliquid therefrom, independent liquid-seal means for the scum duct andfor the conduit means provided exteriorly of the tank for minimizingleakage of air therethrough, the emission terminal section oi the feedinlet means being supported and rotated from said shaft, and thescum-sweeping means being also supported and rotated from said shaft.

12. An apparatus for performing a continuous process for separating andremoving of suspended matter from a liquid which comprises a closed topmain separating tank adapted i'or the establishment therein oi anever-changing main body of liquid for treatment normally maintained at apre-determined liquid level and of a gas-holding portion that directlyroverlies said liquid body whose pressure is maintained substantiallylower than that oi the outside atmosphere; means providing an auxiliaryliquidheight control compartment having a lower liquid-holding portionadapted for the establishment therein ot an auxiliary body o1' liquidderived from the main tank and an overlying gassholding portion; meansdefining a freely communicating gas passageway between said gas-holdingportions; pumping means for removing sas from said gasholding portionsand adapted Vfor maintaining substantially sub-at mospneric pressureconditions therein and comprising on the intake side thereoil pipinghaving suction nomic structure providing nozzle intake means operativelydisposed within the auxiliary liquid-height control compartment adaptedto establish at the elevation ot the nomic intake means the normalliquid level of the body of liquid in the main tank and also to removeany l liquid tending to rise above the :so-established normal liquidlevel; means for continuously sub-1 mergedly delivering a liquid-solidssuspension into the main tank while permitting no substantial leaking ofoutside air yinto the main tank; means for continuously releasing liquidfrom the main tank without permitting any substantial leakage o! outsideair into themain tank; an open top trough located within the main tankhaving a horizontally extending transfer edge at an elevation proximatethat of the nozzle intake means; and means for transferring materialfrom said open top trough to the exterior oi' the apparatus withoutpermitting any substantial leakage of outside air into the tank.

13. An apparatus according to claim 12, also having means for impeilingoatable matter from Ythe surface of the body oi. liquid in the mainYtank towards and over the horizontally extend transfer edge of thetrough and thus into the open top trough.

EARL M. KELLY. ARTHUR M. KIVARI. ROBERT P. KITE. ELLIO'I'I" J. ROBERTS.DAVID B. SUTHERLAND.

